The present invention relates to an optical cross connect apparatus used in an optical transmission system as an apparatus for switching large-capacity lines on an optical layer and adding/dropping such lines. The invention further relates to a network management apparatus for monitoring and controlling the optical cross connect apparatus.
In recent years, broadband lines have been becoming popular also at homes and the demand for the broadband lines for mainly handling IP traffic has been rapidly increasing. Transmission apparatus for handling such a variety of high-speed lines include an OXC (optical cross connect) apparatus and an OADM (Optical Add-Drop Multiplexer). The OXC apparatus has an optical cross connect function for switching routes between a plurality of input/output ports passed through by optical signals by keeping the optical signals unprocessed as they are. On the other hand, the OADM is capable of adding and dropping a variety of lines passed through by optical signals by using a waveform division multiplexing technology with the optical signals unprocessed as they are. Thus, the OXC apparatus and the OADM are transmission apparatus capable of transmitting a received high-velocity and broadband optical signal to a destination by way of a transmission network at a high velocity by handling the received optical signal as it is, carrying out no signal processing on the signal at all and merely switching the route of the optical signal with the signal unprocessed as it is. The signal processing includes a process to terminate and modify data and header of the received optical signal.
The transmission apparatus provided at each node between bases turns on and off a switch employed therein to connect any arbitrary input port of the apparatus to any arbitrary output port thereof. Thus, a network connected to the input port of the transmission apparatus is linked to a network connected to the output port thereof. As a result, an optical path of a service signal can be provided through an arbitrary route between the input and output ports.
These transmission apparatus are characterized in that the apparatus are capable of handling a variety of service optical signals exchanged between users and changing routes of the optical signals by keeping the optical signals unprocessed as they are without regard to the data type of the signal. The data type of the handled optical signal is expressed in terms of the velocity of the signal, the frame format of the signal, the type of the transmission protocol of the signal and the encoding method of the signal.
The conventional line exchange apparatus has means for detecting an incorrect connection existing between terminals connected to the apparatus at a line exchange time. As a method of detecting an incorrect connection, there are techniques disclosed in Japanese Patent Laid-open No. 2003-219030 and Japanese Patent Laid-open No. Hei 9-074411. In accordance with the method disclosed Japanese Patent Laid-open No. 2003-219030, a specific pattern or identifier is inserted into a received user signal for a collation purpose. In accordance with the method disclosed in Japanese Patent Laid-open No. Hei 9-074411, on the other hand, information such as call control information is exchanged between line exchange apparatus at consecutive times to establish connection between the apparatus.
With these conventional misconnection detection methods, an incorrect connection between lines can be detected only after the line exchange apparatus have already been connected to each other physically and only if interfaces such as the electrical level of an electrical signal flowing through a line connecting the line exchange apparatus match each other. Thus, with the conventional misconnection detection methods, an incorrect connection cannot be determined till the lines are actually connected to each other. That is to say, the conventional misconnection detection methods do not provide means for avoiding such a state of an incorrect connection in advance before setting lines.
As described in patent documents 1 and 2, the conventional line exchange apparatus monitors the state of connection with an adjacent line exchange apparatus and the state of connection inside the line exchange apparatus, that is, the state of connections between input and output ports of the line exchange apparatus. That is to say, these conventional line exchange apparatus do not monitor the state of all connections of lines serving as routes for user signals between input points and output points in a concentrated manner. An input point is a point in a line exchange network comprising a plurality of line exchange apparatus connected to each other. A user signal transmitted by a user terminal enters the line exchange network by way of the input point. An output point is a point from which the user signal leaves the line exchange network, propagating to the terminal of a user serving as a communication partner by way of the line exchange apparatus.